Photothermal probe beam deflection measurement of thermal diffusivity of atmospheric air

We have used a modified photothermal probe beam deflection system with a back pumping configuration for the measurements of the temperature-dependent thermal diffusivity of atmospheric air. The results are consistent and reasonably well agree with the literature values. The measured thermal diffusivity values are the same for the same measuring temperature regardless of the beam offsets and the deflecting surface temperatures. For the gas with known temperature-dependent thermal diffusivity, this method can be used to deduce the temperature of a gas from the measured thermal diffusivity value.     

Organometallic compounds: XXXVII. Bridge rearrangements of multibridged ferrocenophanes in the presence of aluminum chloride

Two bridge-rearrangement reactions with AlCl₃ have been found in the cyclization of [4](1,1′)[3](2,2′)[4](4,4′)ferrocenophanebutanoic acids (XIb and XIIb) and in the Friedel-Crafts acylation of [4](1,1′)-α-oxo[3](2,2′)[4](4,4′)ferrocenophane(I). The cyclization of XIb and XIIb with ClCO₂Et/NEt₃/AlCl₃ gives no tetrabridged ferrocenophane but three dibridged ferrocenophanes (XVII, XVIII and XIX) each containing two six-membered condensed-rings which are formed via homoannular cyclization of the side chains followed by rearrangement of the existing tetramethylene bridges. Various multibridged ferrocenophanes were treated with AlCl₃ to account for the reaction mode in the rearrangement of I, and evidence for selective acyl migration of the oxotrimethylene bridge to the other cyclopentadienyl ring has been obtained.     

Separations of first and second order theories in bounded arithmetic

We prove that PTC_N(n) (the polynomial time closure of the nonstandard natural number n in the model N of S₂.) cannot be a model of U¹₂. This implies that there exists a first order sentence of bounded arithmetic which is provable in U¹₂ but does not hold in PTC_N(n).     

Young American and Chinese Children's Everyday Mathematical Activity

This study examined possible cultural and SES differences in the type, frequency, and complexity of 4- and 5-year-old American and Chinese children's everyday mathematical activities during free play. 60 American children, 30 each from lower- and middle-socioeconomic status (SES) families, and 24 Chinese children, 12 each from lower- and middle-SES families, participated in the study. Each participant was videotaped during free play for 15 min. The results showed that during free play American and Chinese children exhibit similar types of mathematical activity. Yet, Chinese children engage in a considerably greater amount of mathematical activity, particularly pattern and shape, than do American children. However, closer examination revealed that Chinese and American children do not differ in the complexity of mathematical activities. The results failed to reveal significant differences in the frequency and complexity of everyday mathematics between lower- and middle-SES groups in both cultures.     

An Inverse Spectral Problem for a Nonsymmetric Differential Operator: Uniqueness and Reconstruction Formula

We consider an eigenvalue problem for a system on [0, 1]: $$\left\{ {\begin{array}{*{20}l} {\left[ {\left( {\begin{array}{*{20}c} 0 & 1 \\ 1 & 0 \\ \end{array} } \right)\frac{{\text{d}}} {{{\text{d}}x}} + \left( {\begin{array}{*{20}c} {p_{11} (x)} & {p_{12} (x)} \\ {p_{21} (x)} & {p_{22} (x)} \\ \end{array} } \right)} \right]\left( {\begin{array}{*{20}c} {\varphi ^{(1)} (x)} \\ {\varphi ^{(2)} (x)} \\ \end{array} } \right) = \lambda \left( {\begin{array}{*{20}c} {\varphi ^{(1)} (x)} \\ {\varphi ^{(1)} (x)} \\ \end{array} } \right)} \\ {\varphi ^{(2)} (0)\cosh \mu - \varphi ^{(1)} (0)\sinh \mu = \varphi ^{(2)} (1)\cosh \nu + \varphi ^{(1)} (1)\sinh \nu = 0} \\ \end{array} } \right.$$ with constants $$\mu ,\nu \in \mathbb{C}.$$ Under the assumption that p₂₁, p₂₂ are known, we prove a uniqueness theorem and provide a reconstruction formula for p₁₁ and p₁₂ from the spectral characteristics consisting of one spectrum and the associated norming constants.     

Robust Metaheuristic Algorithm for Redundancy Optimization in Large-Scale Complex Systems

Based upon the general tabu search methodology, this paper develops a robust metaheuristic algorithm for the redundancy optimization in large-scale complex system reliability that performs a rigorous search of the “attractive” feasible space and is capable of escaping from a local solution. An illustrative example is provided and extensive computational results are reported on two test problems from the literature (Aggarwal, 1976; Shi, 1987) and also on randomly generated large-scale instances of complex systems with up to 200 components. The computational results indicate that the proposed metaheuristic algorithm possesses a superior robustness and efficiency for solving the class of hard optimization problems studied in this paper.     

The synthesis and properties of a methylviologen analogue

A novel derivative of methylviologen, prepared by transannular reaction of [2.2] (3,5) pyridinophane, shows large bathochromic shift in the electronic spectrum and nearly equal redox potential compared with methylviologen.     

Time-resolved photoinduced absorption spectroscopic study on trapped carriers at semiconductor–glass interfaces

0.4 Se_0.6 microcrystals was investigated by using time-resolved differential transmittance spectroscopy. The electron trapping at microcrystal–glass interfaces was found to occur within less than 1 ps after photoexcitation. At low excitation energy density, the excited electrons are trapped at point defects distributed over the nanocrystal interfaces. Such electrons give rise to long-lived photoinduced absorption with a lifetime of 3.2 ns. On the other hand, at high excitation energy density, transient absorption with a fast (60 ps) and simultaneously a slow decay component (3.2 ns) was observed. This short-lived photoinduced absorption is attributed to the electrons trapped at the shallow trap states of the semiconductor–glass interfaces. Received: 11 September 1996/Accepted: 9 December 1996     

Circuit model for two-electrode AC discharge

This paper presents a circuit model for a two-electrode AC discharge, which has two electrodes separated from the discharge gap by an insulator. The model consists of a series connection of an equivalent circuit for plasma and two capacitors for insulator. The equivalent circuit for plasma was constructed using the measured electrical properties of a two-electrode DC discharge. The validity of model was checked with experiments on a three-electrode test device; two electrodes exposed to the discharge gap and the other electrode separated from the discharge gap by an insulator. The measured voltages of the test device are compared with those obtained by circuit simulation. For various waveforms, which are being used widely to drive an AC plasma display panel, the results of circuit simulation agree well with experiment.     

Variation of Microenvironment around Auramine O Molecules Doped in Silica Prepared from Tetramethoxysilane

Silica gel doped with Auramine O (AuO), which is known as a microscopic viscosity probe through fluorescence spectra, was prepared by the sol-gel method using tetramethoxysilane (TMOS) as a starting alkoxide. Fluorescence spectra from the starting solution to the dry gel were measured to pursue the variation of microscopic viscosity around the AuO molecules during the sol-gel process. The fluorescence intensity of AuO did not change at the gelation point, indicating that the microscopic viscosity around AuO did not change during the sol-to-gel transformation. The intensity was, however, increased largely in the drying process; the internal motion of AuO molecules became largely restricted by the surrounded silica matrix during the drying process.